Re: [PATCH 0/3] builtin/commit-graph.c: new split/merge options

> Hi,
> 
> Here are another few patches that came out of working on GitHub's
> deployment of incremental commit-graphs. These three patches introduce
> two new options: '--split[=<merge-all|no-merge>]' and
> '--input=<source>'.
> 
> The former controls whether or not commit-graph's split machinery should
> either write an incremental commit graph, squash the chain of
> incrementals, or defer to the other options.
> 
> (This comes from GitHub's desire to have more fine-grained control over
> the commit-graph chain's behavior. We run short jobs after every push
> that we would like to limit the running time of, and hence we do not
> want to ever merge a long chain of incrementals unless we specifically
> opt into that.)

> The latter of the two new options does two things:
> 
>   * It cleans up the many options that specify input sources (e.g.,
>     '--stdin-commits', '--stdin-packs', '--reachable' and so on) under
>     one unifying name.
> 
>   * It allows us to introduce a new argument '--input=none', to prevent
>     walking each packfile when neither '--stdin-commits' nor
>     '--stdin-packs' was given.

> Together, these have the combined effect of being able to write the
> following two new invocations:
> 
>   $ git commit-graph write --split=merge-all --input=none
> 
>   $ git commit-graph write --split=no-merge --input=stdin-packs
> 
> to (1) merge the chain, and (2) write a single new incremental.